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  2. General linear group - Wikipedia

    en.wikipedia.org/wiki/General_linear_group

    In mathematics, the general linear group of degree n is the set of n×n invertible matrices, together with the operation of ordinary matrix multiplication.This forms a group, because the product of two invertible matrices is again invertible, and the inverse of an invertible matrix is invertible, with the identity matrix as the identity element of the group.

  3. List of set identities and relations - Wikipedia

    en.wikipedia.org/wiki/List_of_set_identities_and...

    To investigate the left distributivity of set subtraction over unions or intersections, consider how the sets involved in (both of) De Morgan's laws are all related: () = = () always holds (the equalities on the left and right are De Morgan's laws) but equality is not guaranteed in general (that is, the containment might be strict).

  4. List of mathematical proofs - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_proofs

    Fermat's little theorem and some proofs; Gödel's completeness theorem and its original proof; Mathematical induction and a proof; Proof that 0.999... equals 1; Proof that 22/7 exceeds π; Proof that e is irrational; Proof that π is irrational; Proof that the sum of the reciprocals of the primes diverges

  5. Schur's lemma - Wikipedia

    en.wikipedia.org/wiki/Schur's_lemma

    In mathematics, Schur's lemma [1] is an elementary but extremely useful statement in representation theory of groups and algebras.In the group case it says that if M and N are two finite-dimensional irreducible representations of a group G and φ is a linear map from M to N that commutes with the action of the group, then either φ is invertible, or φ = 0.

  6. Lie algebra - Wikipedia

    en.wikipedia.org/wiki/Lie_algebra

    It is called the general linear Lie algebra. When F is the real numbers, g l ( n , R ) {\displaystyle {\mathfrak {gl}}(n,\mathbb {R} )} is the Lie algebra of the general linear group G L ( n , R ) {\displaystyle \mathrm {GL} (n,\mathbb {R} )} , the group of invertible n x n real matrices (or equivalently, matrices with nonzero determinant ...

  7. Combinatorial proof - Wikipedia

    en.wikipedia.org/wiki/Combinatorial_proof

    An archetypal double counting proof is for the well known formula for the number () of k-combinations (i.e., subsets of size k) of an n-element set: = (+) ().Here a direct bijective proof is not possible: because the right-hand side of the identity is a fraction, there is no set obviously counted by it (it even takes some thought to see that the denominator always evenly divides the numerator).

  8. Back-and-forth method - Wikipedia

    en.wikipedia.org/wiki/Back-and-forth_method

    As an example, the back-and-forth method can be used to prove Cantor's isomorphism theorem, although this was not Georg Cantor's original proof. This theorem states that two unbounded countable dense linear orders are isomorphic. [1] Suppose that (A, ≤ A) and (B, ≤ B) are linearly ordered sets;

  9. MacMahon's master theorem - Wikipedia

    en.wikipedia.org/wiki/MacMahon's_Master_theorem

    In 1962, Good found a short proof of Dixon's identity from MMT. In 1969, Cartier and Foata found a new proof of MMT by combining algebraic and bijective ideas (built on Foata's thesis) and further applications to combinatorics on words, introducing the concept of traces. Since then, MMT has become a standard tool in enumerative combinatorics.